Although it trails Red Bull and Monster in terms of market share, Rockstar is the energy drink generating headlines this week — for its ability to spike blood pressure and increase levels of a "fight or fight" stress hormone in the body, according to a study published in the Journal of the American Medical Association.

"The increases in blood pressure are accompanied by increases in norepinephrine, a stress hormone chemical, and this could predispose an increased risk of cardiac events – even in healthy people," lead author, Dr. Anna Svatikova, a Mayo Clinic cardiology fellow, noted in the press release.

Just one 16-ounce can of Rockstar — which contains 240mg of caffeine; 2,000mg of taurine; and extracts of guarana seed, ginseng root, and milk thistle — increased norepinephrine by 74 percent and blood pressure by 6.4 percent in 25 healthy volunteers, 14 of them male, with a mean age of 29. These numbers, say the researchers, are worrisome.

Norepinephrine affects the part of the brain that controls our attention and reactions and triggers our "fight or flight" stress response. Spikes in stress hormones such as norepinephrine can trigger all sorts of responses in the body that can negatively affect health, such as increasing heart rate, blood pressure, blood flow, and making breathing more rapid.

This isn't the first time experts have voiced concerns about energy drinks. Dr. Kent Sepkowitz noted in previous research published in JAMA in 2013 that coffee and many soft drinks and energy drinks typically contain 100mg of caffeine per serving; some energy drinks, such as Rockstar, have as much as 250mg. "The millions of persons consuming energy drinks … may be unaware of the amount of caffeine they are ingesting,” said Sepkowitz. "Consequently, unintentional caffeine overdoses have resulted in serious illnesses and rare deaths from caffeine poisoning.”

Indeed, energy drink–related emergency room visits doubled between 2007 and 2011, according to a 2013 report issued by the Substance Abuse and Mental Health Service Administration (SAMHSA) that called the spike "a continuing public health concern." The report also noted, however, that the biggest increase in visits was among energy drink consumers over 40 years old, and only 58 percent of the 2011 visits involved only energy drinks; 42 percent went to the emergency room for mixing energy drinks with other drugs.